COLOUR AT DIFFERENT ELEVATIONS. 511 is actually destroyed by bright light in plants which are not properly screened, and the green tissue is then blanched and assumes a yellow tint. Since the intensity of the sun's rays increases with the elevation in mountain districts (see vol. i. p. 525), we should expect that this effect of light would be shown particularly well in plants of high elevation. And this is certainly the case. The flowers of species grown in the Alpine garden on the Blaser at a height of 2195 metres above the sea exhibited, as a rule, brilliant floral tints, and some were decidedly darker than the flowers grown in the Vienna Botanic Garden. Agrostemma Githago, Gamipanula pusilla, Bianthus inodorus (sylvestris), GypsoŽ phila repens, Lotus corniculatus, Saponaria ocymoides, Satureja hortensis, Taraxacum officinale, Vicia Cracca, and Vicia sepium are good examples of this. Several species, which produced pure white petals in the Vienna gardens, e.g. Libanotis montana, had petals coloured reddish-violet by anthocyanin on their under sides in the Alpine garden. The glumes of all the Grasses which were green, or only just tinged with violet at a low level became a dark brownish- violet in the Alpine garden. The abundant formation of anthocyanin in the green tissue of the foliage-leaves and sepals, and in the stem, was particularly apparent. The leaves of the Stonecrops, Sedwm acre, album, and sexangulare became purple-red, those of Bracocephalum Ruyschianum and Leucanthemum vulgare violet, those of Lychnis Viscaria and Satureja hortensis a brownish- red, and the foliage-leaves of Bergenia crassifolia and Potentilla Tiroliensis, even in August, had the scarlet-red colour which they usually assume in sunny spots in the valley in late autumn. I must not omit to mention that, according to some of my zoological friends, many animals, especially spiders and snails, which have been transferred from the plains to the mountain-heights, assume a darker tint in alpine regions. A considerable number of plant species, especially those which grow in the valley in shaded or half-shaded places, as, for example, Arabis procurrens, Digitalis ochroleuca, Geum urhanum, Orohus vernus, Valeriana Phu, and V. simpUcifoUa, Viola cucuUata, developed more or less yellowish leaves in the Alpine garden, where they were exposed to the full sunlight. It was mentioned in vol. i. p. 393, that the Flax (Linum usitatissim,um), which flourishes in mountain valleys at a height of 1500 metres, where its chlorophyll is uninjured, nevertheless turns yellow in the Alpine garden at a height of 2195 metres; From this general review of the modiflcations in plant-form obtained by culture-experiments, a series of important conclusions may naturally be drawn. In the first place we must point out that two kinds of characters are to be observed in plants, those which are the result of certain conditions and properties of soil and climate, and those which appear independently of these external influences. This distinction is so important that we shall illustrate it by two examples. The white Water-lily, Nym/phcm alba, develops scale-leaves of ovate or lanceolate shape with no separation into petiole and lamina. The foliage-leaves, however.